Apparently Lion Turtles provided humans the power of the elements and mere beasts were the "teachers". Spirits didn't do anything. Spirits didn't create the human kind and the physical world, but they entered in after Vaatu broke the barrier of two paraller words making spirits to enter the physical world and disrupt the balance there. So the problem are the spirits, not the humans there.

Besides those fictional humans knew the ability of Energybending before the spirits came and ruined everything. So, the spirits are dumb and dangerous unstable creatures and humans are sapient and setient. Spirits are freaks of nature and they damaged the judgement of human when they entered there making humans xenophobic and isolated. Spirits in that fictional verse are also big dochebags. Reminds you of something familiar?